M3: Agent bound to a seat — configure an AI seat

OrgBoard: Agent entity (name, monogram, autonomy dial, ApiConfigId + optional fallback,
skill keys, docs) + AddAgents migration; one agent per seat. References Skills by key and
the BYOK config by id — never reaches into those modules.

Endpoints: POST/GET /api/orgboard/seats (create/list seats), POST/GET
/api/orgboard/seats/{id}/agent (configure/read the agent) — ConfigureAgents at [team, org].
Configuring an agent flips the seat to the AI state and points it at the agent; audited.

Verified: build green; ArchitectureTests 8/8; IntegrationTests 27/27 incl. the M3 acceptance
flow — owner adds a BYOK config, then configures "Aria" (gated autonomy, skills, that config)
on a seat, flipping it to AI, with the key never exposed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Modules/TeamUp.Modules.OrgBoard/Endpoints/OrgBoardDtos.cs

@@ -1,4 +1,5 @@
 using TeamUp.Modules.OrgBoard.Domain;
+using TeamUp.SharedKernel.Access;
 
 namespace TeamUp.Modules.OrgBoard.Endpoints;
 
@@ -30,3 +31,27 @@ internal sealed record TaskResponse(
 internal sealed record BoardColumn(string Status, IReadOnlyList<TaskResponse> Items);
 
 internal sealed record BoardResponse(Guid TeamId, IReadOnlyList<BoardColumn> Columns);
+
+internal sealed record CreateSeatRequest(Guid TeamId, string RoleName);
+
+internal sealed record SeatResponse(Guid Id, Guid TeamId, string RoleName, string State, Guid? MemberId, Guid? AgentId);
+
+internal sealed record ConfigureAgentRequest(
+    string Name,
+    string? Monogram,
+    Autonomy Autonomy,
+    Guid ApiConfigId,
+    Guid? FallbackApiConfigId,
+    List<string> SkillKeys,
+    List<string> Docs);
+
+internal sealed record AgentResponse(
+    Guid Id,
+    Guid SeatId,
+    string Name,
+    string? Monogram,
+    string Autonomy,
+    Guid ApiConfigId,
+    Guid? FallbackApiConfigId,
+    List<string> SkillKeys,
+    List<string> Docs);